Photosynthesis in space


Designing a magic box that measures how much photosynthetic microorganisms manage to release O2 and "clean up" atmospheres with high levels of CO2 in non-terrestrial conditions.

Like plants, photosynthetic microorganisms can reduce CO2 from the atmosphere and convert it into edible biomass, while also emitting O2. However, unlike plants they have fewer demands for growth and can thrive in extreme environmental conditions. The study of their photosynthetic abilities in simulated non-terrestrial environments will offer fundamental support for the success of future space missions as well as contributing to the development of new biotechnological processes.

A team of multidisciplinary researchers from Padua has designed a new experimental setup that will allow the non-invasive study of the responses of photosynthetic microorganisms to simulated non-terrestrial conditions. Nicoletta La Rocca of the University of Padua’s Department of Biology, Luca Poletto of the Institute of Photonics and Nanotechnology of the CNR IFN, and Riccardo Claudi of the INAF Astronomical Observatory of Padua coordinated the setup jointly. The research work was published in the journal “Frontiers in Plant Science” under the Research topic Higher Plants, Algae and Cyanobacteria in Space Environments entitled “A new remote sensing-based system for the monitoring and analysis of growth and gas exchange rates of photosynthetic microorganisms under simulated non-terrestrial conditions”.

The setup, designed and created by the team, consists of two main components: a Star Light Simulator (SLS) that allows you to accurately generate the light spectra emitted by different classes of stars and a Simulator Chamber where cultures of non-atmospheres terrestrial (ASC) grow photosynthetic microorganisms by simultaneously illuminating them with the selected star lights. The setup is equipped remotely and continuously with sensors that measure the photosynthetic parameters of microorganisms. The measurements include the consumption of carbon dioxide (CO2) and the release of oxygen (O2), without the need to open the growth chamber and therefore without changing the non-terrestrial conditions to which they are exposed. A Reflectivity Detection System (RDS) is used to measure the Normalized Difference Vegetation Indexes (NDVI) taken from the measurements of light reflected by organisms. This system applies a technology normally used by satellite systems to monitor terrestrial vegetation levels in the laboratory. Growing crops of cyanobacteria validated the setup, as this microorganism is responsible for the appearance of oxygen photosynthesis, which since it is based on oxygen, allows for the evolution of life, as is known on earth.

In a statement from the three researchers Nicoletta La Rocca, Luca Poletto and Riccardo Claudi “The setup is quite innovative and its realization was made possible thanks to the extensive work and sharing of specific skills in astrophysical, engineering, physical-chemical and biological fields”. Nicoletta La Rocca of the Department of Biology of the University of Padua underlines that “the tool can be used in both applied and basic research and with this setup it will be possible to evaluate a photosynthetic microorganisms ability to ‘clean up’ atmospheres within a high concentrations of CO2 by taking this gas and converting it into biomass”. This will contribute to the development of new technologies in the field of bio regenerative life support systems for human space exploration. Furthermore, in regards to basic research, the setup will allow researchers to better define the limits of photosynthesis and therefore oxygen based life in lighting conditions and atmospheric compositions beyond terrestrial ones. La Rocca continues, “These studies will open important perspectives for the search for signs of life in extra-solar planets. Experiments of exposure of cyanobacteria to simulated light conditions of dwarf red stars and oxygen-free atmospheres are already underway.

These studies will be of great importance to understand if earth-like planets (terrestrial and super-earth planets), which have been discovered to rotate around dwarf red stars such as the famous TRAPPIST-1 and Proxima Centauri, could allow for oxygen photosynthesis and consequently the evolution of life. The data obtained from these measurements can be compared to the measurements of the atmospheric compositions of these earth-like planets in foreseen space missions”.

The study was partly funded by the Italian Space Agency under the "Life in space" project with the specific objective of studying the answers of photosynthetic microorganisms with simulated lights of dwarf red stars, and is under the responsibility of Nicoletta La Rocca and the research unit in Padua.